This application claims the benefit of Japanese Patent Application No. 2006-263324 filed on Sep. 27, 2006, the entirety of which is incorporated by reference.
1. Field of the Invention
The present invention relates to an electrically-operated chuck opening-closing device that opens and closes a chuck provided to a main spindle of a machine tool by an electrically-operated drive device.
2. Background Art
As machine tools such as lathes and the like, chuck opening-closing type machine tools with a chuck for gripping a workpiece (work) provided to the tip of the main spindle is known. Since a conventional chuck opening-closing type machine tool opens and closes the chuck by a hydraulic cylinder, there has been a problem in that not only a hydraulic cylinder is required but also hydraulic oil must be periodically changed. In addition, since the pump must be constantly operated to maintain oil pressure during processing, there is a problem of large energy consumption. In addition, there has been a problem in that the temperature rises due to heat generated by the hydraulic cylinder and degrades the processing accuracy of the workpiece. Furthermore, in the case of processing where the chuck gripping force must be changed during rotation of the main spindle as is the case with thin-walled workpiece, the rotation of the main spindle must be temporarily stopped and the chuck gripping force must be changed; this causes the operation to be troublesome and requires long time for processing.
Consequently, as disclosed in patent document 1, an electrically-operated chuck opening-closing mechanism is devised in which an auxiliary motor is provided for opening and closing the chuck independently of the motor for rotating and driving the main spindle, and the chuck gripping force can be controlled during rotation of the main spindle by the auxiliary motor. In addition, as disclosed in patent document 2, an electrically-operated chuck opening-closing mechanism is devised, which includes a gear mechanism to open and close the chuck via a draw-tube through which the inside of the main spindle is inserted and a clutch that can couple and decouple the gear mechanism to and from an auxiliary motor.
[Patent document 1]
Japanese Patent Application Laid-Open Publication No. 58-217204
[Patent document 2]
Japanese Patent Application Laid-Open Publication No. 2001-246510